JP2014238598A - Liquid crystal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal device exhibiting image characteristics with high contrast and a wide viewing angle and fast in-plane switching and permitting display of moving images.SOLUTION: The liquid crystal device is driven by a linear coupling such as ferroelectric coupling and/or flexoelectric coupling between an inhomogeneous in-plane electric field generated by an electrode pattern 41, 42 over a first sub-volume of a bulk layer 44 adjacent to the electrode pattern 41, 42 and liquid crystals in a polarized state included in the first sub-volume and/or in an alignment layer 43 applied on the electrode pattern 41, 42. The polarization is stronger than any liquid crystal polarization of the bulk layer, outside (i) the first sub-volume and the alignment layer (43), and outside (ii) a second sub-volume of the bulk layer adjacent to an inner surface of the other substrate, or a second alignment layer or a second electrode pattern applied thereon.

Description

  The present invention relates generally to the technical field of liquid crystals, and more particularly, the present invention relates to linear coupling, such as ferroelectric coupling and / or, between liquid crystals that are in a polarized state and within an applied in-plane electric field. Alternatively, the present invention relates to a liquid crystal device driven by flexoelectric coupling.

(Technical background)
In general, nematic liquid crystal displays (LCDs) operate on the basis of dielectric coupling, such as the dielectric anisotropy (Δε) of the liquid crystal and the applied electric field that produces an electro-optic response. This response is expressed by a quadratic expression of the applied electric field. That is, it is not polar, but results from switching of liquid crystal molecules by an electric field. In a conventional nematic LCD, the switching of liquid crystal molecules occurs in a plane that includes the direction of the applied electric field. Thereby, an electric field applied across the liquid crystal sandwich cell causes the molecules to switch out of plane, i.e. in a plane perpendicular to the cell substrate. However, this type of switching produces an electro-optic response with a contrast that is highly dependent on the viewing angle. Furthermore, the total response time (τ), ie the switching time, which is the sum of the rise time (τ _r ) and the fall time (field off) time (τ _f ), is usually short enough to display a moving image. It can not be said.

  On the other hand, an LCD having a pattern in which electrodes deposited on one inner surface of the substrate (generating an in-plane electric field) are staggered causes in-plane switching (IPS) of the optical axis, and thus contrast. Provides images that are less dependent on viewing angle. In an improved version, S-IPS (Super In-plane Switching), a herringbone electrode structure is used. Nevertheless, the switching time of a display operating in this IPS-mode is not short enough to produce high quality moving images.

  An in-plane electric field can be effectively generated by the comb-like electrode structure that generates a fringe electric field. However, in these so-called fringe field switching (FFS) devices, dielectric coupling is generally used, and thus the problem that the electric field off time becomes long is not solved.

In the above case, the electric field off time (τ _f ) does not depend on the magnitude of the applied electric field, but the rise time (τ _r ) depends on the magnitude of the applied electric field. Therefore, the rise time can be efficiently controlled by the electric field, but the electric field off time is independent of the electric field. This field off time is determined not only by cell characteristics, eg, cell gap, but also by liquid crystal material parameters, eg, viscosity and anchor strength to the solid substrate.

  Another known method for switching nematic liquid crystals to different optical states utilizes a linear coupling between the flexoelectric bulk polarization of the initially deformed nematic liquid crystal and the applied electric field. (Dozov et al., “Flexoelectrically controlled twist texture in nematic liquid crystal”, Journal de Physic Letter 43 (1982), L-365 to L-369 (Non-patent Document 1) , And Komitov et al., "New Polarized Electro-Optical Effects in Reversibly Pretilted Nematic Liquid Crystal Layers with Weak Anchoring," Minutes of the Third International Display Research Conference, November 1983, Kobe, Japan (Non-Patent Document 2)).

  International Patent Application No. 2005/071477 describes a liquid crystal comprising a flexoelectric liquid crystal bulk layer in which a pattern of staggered electrodes generates an inhomogeneous electric field in a direction substantially parallel to the substrate. Describes the device. The average polarization direction in the direction parallel to the substrate in the electric field off state is preferably orthogonal to the direction in which the electric field should be generated. In this case, both the rise time and the fall time are determined by the electric field, and the total response time is shortened.

  U.S. Pat. No. 6,160,600 describes a liquid crystal display device in which a display electrode and a common electrode are disposed on one of two substrates. The direction of the liquid crystal material is a HAN (hybrid alignment nematic) type. In this device, a liquid crystal material having a high dielectric constant is required because the liquid crystal material near the substrate provided with the electrodes is switched by dielectric coupling to an electric field. Furthermore, this mode of switching does not allow switching directivity control.

  Ferroelectric liquid crystal (FLC) display devices including comb-like electrodes are also known (Japanese Published Patent JP 10-161128, Patent Document 3).

  Recently, in-plane switching of nematic liquid crystals has been realized by applying an electric field across the cell substrate by using an electrically commanded surface (PCS). Published international patent application WO 00/03288 describes the so-called electrically commanded surface (ECS) principle.

According to the ECS principle, a separate chiral smectic liquid crystal thin film, preferably a ferroelectric (chiral smectic C phase, SmC ^* ) liquid crystalline, on the inner surface of one or both of the substrates confining the liquid crystal bulk material in a conventional sandwich cell. A polymer film is deposited.

  This chiral smectic liquid crystalline polymer layer acts as a surface-induced alignment layer that aligns the adjacent liquid crystal bulk material in a planar or substantially planar manner. More specifically, when an external electric field is applied to both ends of the cell, and thus to both ends of the surface-induced alignment film, the molecules in the separate chiral smectic liquid crystalline layer are switched. This change in the dynamic surface-induced alignment film in response to the electric field is referred to as “primary surface switching”. As a result of this primary surface switching, preferred molecular orientation switching then occurs in the bulk volume of the liquid crystal bulk material confined between the substrates via elastic forces (steric bonds). This secondary switching is referred to as “inductive bulk switching”. This inductive bulk switching is in-plane switching. Therefore, the switching of molecules in the dynamic surface-induced alignment film is transferred into the bulk volume via elastic force at the boundary between the separate surface-induced alignment film and the bulk layer, resulting in dynamic surface induction. A relatively fast in-plane switching of the bulk volume molecules transmitted by the alignment film occurs.

The chiral smectic liquid crystalline layer, ie the dynamic surface-induced alignment film, is a chiral smectic or anti-clinic chiral smectic, eg a smectic C (SmC ^* or SmC _A ^* ) material, or a chiral smectic A (SmA containing random SmC ^* ). ^* ) Materials can be used. Accordingly, the dynamic surface-induced alignment film response to an applied electric field can be ferroelectric, antiferroelectric, or paraelectric, respectively.

  Published international patent application WO2003 / 081326 includes a liquid crystal bulk layer and a chiral dopant distributed non-homogeneously in the bulk layer as a result of being permanently attached to at least one surface. A liquid crystal device is described in which the dopant induces spontaneous polarization in a sub-volume of the bulk layer adjacent to the surface. The response of the bulk layer in the subvolume to the electric field applied to the bulk layer can be ferroelectric, antiferroelectric or paraelectric.

  Using an ECS layer / subvolume in a liquid crystal device provides fast in-plane switching and relatively high image contrast. However, it is desirable to improve the contrast more uniformly and the required voltage is considerably higher.

International Patent Application No. 2005/071477 US Pat. No. 6,160,600 Japanese published patent JP10-161128 International Patent Application No. WO00 / 03288 International Patent Application No. WO2003 / 081326

Dozov et al., “Flexoelectrically controlled twist texture in nematic liquid crystals”, Journal de Physic Letter 43 (1982), L-365 to L-369. Komitov et al., “A novel polar electro-optic effect in a reversibly pretilted nematic liquid crystal layer with weak anchoring”, Proceedings of the 3rd International Display Research Conference, November 1983, Kobe, Japan Paper by D Flanders, D Shaver and H Smith, Applied Physics Letters, 55, 2506 (1978) J Chen and G Boyd, Applied Physics Letters, 35, 444 (1979) GP Bryan-Brown, C V Brown, I C Sage and V C Hull, Nature, V392, 365 (1998) C. Brown, M. Touler, V. Huy, and G. Brian-Brown, Liquid Crystals, 27, 233 (2000) R Caputo, L Dosio, AV Suchaf, A Wertri and C Umeton's paper, Optics Letters, 29, 1261 (2004) G Strangi, V Burna, R Caputo, A Dolka, C Versace, N Skalazza, C Umeton, and R Bartolino, Physical Review Letters, 94, 63903 (2005)

  It is a general object of the present invention to provide an improved liquid crystal device that solves the above problems. In particular, the object of the present invention is the ability to produce images with high contrast and wide viewing angle and the ability to show in-plane fast switching, and more particularly to reduce the fall time of the electro-optic response, and thus An object of the present invention is to provide a liquid crystal device that shortens the total switching time and enables satisfactory display of moving images.

  Another object of the present invention is to reduce the threshold voltage for transmitting the switching of the liquid crystal bulk, that is, to reduce the driving voltage of the liquid crystal device. This is particularly important in portable applications such as mobile phones.

  The present invention is not limited to displays, but can be effective in many other liquid crystal devices.

According to a first aspect of the present invention, the present invention comprises first and second confinement substrates;
A liquid crystal bulk layer disposed between the substrates, a first electrode pattern applied to an inner surface of the first substrate, and a bulk surface of the bulk layer disposed to interact with the bulk layer. And a first alignment film applied to the first electrode pattern, wherein the first electrode pattern has a non-uniform electric field with respect to the first sub-volume part of the bulk layer adjacent to the first alignment film. The electric field is not uniform with respect to the direction of the lines of electric force and the electric field strength, and the electric field provides a liquid crystal device that is also generated for the first alignment film. The device further comprises a liquid crystal in a polarization state contained in the first sub-volume and / or in the first alignment film, wherein the polarization of the liquid crystal is: (i) the first sub-volume and / or the Outside the first alignment film, and (ii) outside the second subvolume of the bulk layer adjacent to the second substrate and / or adjacent to the second alignment film disposed on the second substrate, The liquid crystal in a polarized state, which is stronger than a similar liquid crystal polarization that can occur in the bulk layer and is contained in the first sub-volume and / or in the first alignment film, is between the electric field and the polarization. The coupling is at least partially switched, and the bulk liquid crystal switching is achieved by elastic force.

  Other aspects, features and advantages of the present invention will become apparent from the following description of the invention.

1 is a schematic illustration of a staggered pattern of electrodes for implementation in a device according to the invention. FIG. 2 is a schematic cross-sectional view of an in-plane electric field generated by the staggered pattern of electrodes shown in FIG. FIG. 2 is a schematic cross-sectional view of an electrode structure including comb-like electrodes for generating a fringe electric field in a device according to the present invention. FIG. 6 is a schematic cross-sectional view showing how flexoelectric polarization can be induced at one of the substrate surfaces by the surface topology and / or the anchoring properties of the alignment layer in the device according to the invention. FIG. 6 is a schematic cross-sectional view showing how flexoelectric polarization can be induced at one of the substrate surfaces by the surface topology and / or the anchoring properties of the alignment layer in the device according to the invention. FIG. 6 is a schematic cross-sectional view showing how flexoelectric polarization can be induced at one of the substrate surfaces by the surface topology and / or the anchoring properties of the alignment layer in the device according to the invention. FIG. 6 is a schematic cross-sectional view showing how flexoelectric polarization can be induced at one of the substrate surfaces by the surface topology and / or the anchoring properties of the alignment layer in the device according to the invention. FIG. 6 is a schematic cross-sectional view showing how flexoelectric polarization can be induced at one of the substrate surfaces by the surface topology and / or the anchoring properties of the alignment layer in the device according to the invention. FIG. 6 is a schematic cross-sectional view showing how flexoelectric polarization can be induced at one of the substrate surfaces by the surface topology and / or the anchoring properties of the alignment layer in the device according to the invention. FIG. 6 is a schematic cross-sectional view showing how flexoelectric polarization can be induced at one of the substrate surfaces by the surface topology and / or the anchoring properties of the alignment layer in the device according to the invention. FIG. 6 is a schematic cross-sectional view showing how flexoelectric polarization can be induced at one of the substrate surfaces by the surface topology and / or the anchoring properties of the alignment layer in the device according to the invention. FIG. 6 is a schematic cross-sectional view showing how flexoelectric polarization can be induced at one of the substrate surfaces by the surface topology and / or the anchoring properties of the alignment layer in the device according to the invention. FIG. 6 is a schematic cross-sectional view showing how flexoelectric polarization can be induced at one of the substrate surfaces by the surface topology and / or the anchoring properties of the alignment layer in the device according to the invention. FIG. 6 is a schematic cross-sectional view showing how flexoelectric polarization can be induced at one of the substrate surfaces by the surface topology and / or the anchoring properties of the alignment layer in the device according to the invention. FIG. 4 is a schematic cross-sectional view showing how flexoelectric polarization can be induced at each inner surface of a substrate by surface topology and / or anchoring properties of an alignment layer in a device according to the present invention. FIG. 6 is a schematic cross-sectional view showing how flexoelectric polarization can be induced at one of the substrate surfaces by the surface topology and / or the anchoring properties of the alignment layer in the device according to the invention. FIG. 6 is a schematic cross-sectional view showing how flexoelectric polarization can be induced at one of the substrate surfaces by the surface topology and / or the anchoring properties of the alignment layer in the device according to the invention. FIG. 6 is a schematic cross-sectional view showing how flexoelectric polarization can be induced by a wall dividing the gap of the device in a number of cells in a device according to the present invention. FIG. 6 is a schematic cross-sectional view showing how flexoelectric polarization can be induced by a wall dividing the gap of the device in a number of cells in a device according to the present invention. Fig. 3 shows the structure and performance of a device according to the invention comprising a nematic bulk layer with hybrid orientation (HAN) and staggered electrodes. Fig. 3 shows the structure and performance of a device according to the invention comprising a nematic bulk layer with hybrid orientation (HAN) and staggered electrodes. Fig. 3 shows the structure and performance of a device according to the invention comprising a nematic bulk layer with hybrid orientation (HAN) and staggered electrodes. Fig. 3 shows the structure and performance of a device according to the invention comprising a nematic bulk layer with hybrid orientation (HAN) and staggered electrodes. Fig. 3 shows the structure and performance of a device according to the invention comprising a nematic bulk layer with hybrid orientation (HAN) and staggered electrodes. Fig. 3 shows the structure and performance of a device according to the invention comprising a nematic bulk layer with hybrid orientation (HAN) and staggered electrodes. Figure 2 shows the structure and performance of a device according to the invention comprising a nematic bulk layer with inverted hybrid orientation (HAN) and staggered electrodes. Figure 2 shows the structure and performance of a device according to the invention comprising a nematic bulk layer with inverted hybrid orientation (HAN) and staggered electrodes. Figure 2 shows the structure and performance of a device according to the invention comprising a nematic bulk layer with inverted hybrid orientation (HAN) and staggered electrodes. Figure 2 shows the structure and performance of a device according to the invention comprising a nematic bulk layer with inverted hybrid orientation (HAN) and staggered electrodes. Figure 2 shows the structure and performance of a device according to the invention comprising a nematic bulk layer with inverted hybrid orientation (HAN) and staggered electrodes. Figure 2 shows the structure and performance of a device according to the invention comprising a nematic bulk layer with inverted hybrid orientation (HAN) and staggered electrodes. Fig. 4 shows the structure and performance of a device according to the invention comprising a ferroelectric alignment film and staggered electrodes. Fig. 4 shows the structure and performance of a device according to the invention comprising a ferroelectric alignment film and staggered electrodes. Fig. 4 shows the structure and performance of a device according to the invention comprising a ferroelectric alignment film and staggered electrodes. Fig. 4 shows the structure and performance of a device according to the invention comprising a ferroelectric alignment film and staggered electrodes. Fig. 4 shows the structure and performance of a device according to the invention comprising a ferroelectric alignment film and staggered electrodes. Figure 2 shows the structure and performance of a device according to the invention comprising a nematic bulk layer with inverted hybrid orientation (HAN) and an electrode pattern that generates a fringe electric field. Figure 2 shows the structure and performance of a device according to the invention comprising a nematic bulk layer with inverted hybrid orientation (HAN) and an electrode pattern that generates a fringe electric field. Figure 2 shows the structure and performance of a device according to the invention comprising a nematic bulk layer with inverted hybrid orientation (HAN) and an electrode pattern that generates a fringe electric field. Figure 2 shows the structure and performance of a device according to the invention comprising a nematic bulk layer with inverted hybrid orientation (HAN) and an electrode pattern that generates a fringe electric field. Figure 2 shows the structure and performance of a device according to the invention comprising a nematic bulk layer with inverted hybrid orientation (HAN) and an electrode pattern that generates a fringe electric field. Figure 2 shows the structure and performance of a device according to the invention comprising a nematic bulk layer with inverted hybrid orientation (HAN) and an electrode pattern that generates a fringe electric field. Figure 2 shows the structure and performance of a device according to the invention comprising a nematic bulk layer with inverted hybrid orientation (HAN) and an electrode pattern that generates a fringe electric field. Figure 2 shows the structure and performance of a device according to the invention comprising a nematic bulk layer with inverted hybrid orientation (HAN) and an electrode pattern that generates a fringe electric field. Fig. 2 shows the structure and performance of a device according to the invention comprising a ferroelectric alignment film and an electrode pattern for generating a fringe electric field. Fig. 2 shows the structure and performance of a device according to the invention comprising a ferroelectric alignment film and an electrode pattern for generating a fringe electric field. Fig. 2 shows the structure and performance of a device according to the invention comprising a ferroelectric alignment film and an electrode pattern for generating a fringe electric field. Fig. 2 shows the structure and performance of a device according to the invention comprising a ferroelectric alignment film and an electrode pattern for generating a fringe electric field. Fig. 2 shows the structure and performance of a device according to the invention comprising a ferroelectric alignment film and an electrode pattern for generating a fringe electric field. Fig. 2 shows the structure and performance of a device according to the invention comprising a ferroelectric alignment film and an electrode pattern for generating a fringe electric field. FIG. 2 shows the structure and performance of a device comprising a ferroelectric alignment film and an electrode structure that generates an electric field throughout the bulk. FIG. 2 shows the structure and performance of a device comprising a ferroelectric alignment film and an electrode structure that generates an electric field throughout the bulk. Fig. 2 shows the structure and performance of a device according to the invention comprising a ferroelectric alignment film and an electrode pattern for generating a fringe electric field. Fig. 2 shows the structure and performance of a device according to the invention comprising a ferroelectric alignment film and an electrode pattern for generating a fringe electric field. Fig. 2 shows the structure and performance of a device according to the invention comprising a ferroelectric alignment film and an electrode pattern for generating a fringe electric field. An example of a top electrode structure used in an electrode pattern for generating a fringe electric field in a device according to the present invention is shown. An example of a top electrode structure used in an electrode pattern for generating a fringe electric field in a device according to the present invention is shown. An example of a top electrode structure used in an electrode pattern for generating a fringe electric field in a device according to the present invention is shown. FIG. 6 illustrates an example of a device including an electrode pattern that generates a fringe electric field filled with other nematics oriented perpendicular to the substrate. Fig. 4 shows an example of a top electrode structure used in an electrode pattern for generating a fringe electric field in a device according to the present invention.

(Detailed description of the invention)
The present invention includes first and second confinement substrates;
A liquid crystal bulk layer disposed between the substrates;
A first electrode pattern applied to an inner surface of the first substrate;
The bulk surface of the bulk layer is configured to interact with the bulk layer, and includes a first alignment film applied to the first electrode pattern,
The first electrode pattern is disposed to generate an inhomogeneous electric field over the first subvolume of the bulk layer adjacent to the first alignment layer, and the electric field is homogeneous with respect to the direction of electric field lines and electric field strength. In addition, the electric field is a liquid crystal device generated for the first alignment film,
The liquid crystal in the polarization state is further included in the first sub-volume section and / or the first alignment film, and the polarization of the liquid crystal is (i) the first sub-volume section and / or the first alignment. Any of the bulk layer outside the film, and (ii) outside the second subvolume of the bulk layer adjacent to the second substrate and / or a second alignment film disposed on the second substrate The liquid crystal in a polarized state, which is stronger than similar liquid crystal polarization that can occur and is contained in the first sub-volume and / or in the first alignment film, is at least due to the coupling between the electric field and the polarization. The present invention relates to a liquid crystal device that is partially switched and in which the liquid crystal switching of the bulk layer is achieved by elastic force.

  When the device includes the (first) alignment film applied to the (first) electrode pattern, it can be understood that the first sub-volume portion is adjacent to the (first) alignment film.

  In the absence of an electric field (i.e., no electric field), it is desirable that polarization and / or orientation of the subvolume is present.

  As used herein, when comparing the intensity of polarization inside the subvolume and / or alignment film with the polarization intensity in the bulk layer outside the first and second subvolumes and alignment film The term “similar polarization” refers to polarization that produces the same type of electrical coupling, eg, ferroelectric coupling or flexoelectric coupling.

  As used herein, the term “adjacent to” in relation to a subvolume of liquid crystal bulk material adjacent to a substrate includes the portion of the bulk material where the subvolume is located closest to the substrate. It is related to that. This term does not exclude the possibility that additional components of the device of the present invention, such as electrode patterns and alignment films, can be placed between such subvolumes and the substrate.

  This alignment film is either a passive alignment film or a dynamic alignment film.

  When the alignment film includes the liquid crystal in a polarized state, the alignment film is coupled with the applied electric field to perform switching of the liquid crystal, so that the alignment film can be referred to as a dynamic alignment film. The device according to the invention can comprise a passive alignment film applied to one or both of the substrate surfaces in addition or instead.

  Since the electric field is generated by an electrode pattern that includes electrodes applied to the same substrate surface, the electric field is substantially localized near the substrate surface that supports the electrode pattern. Therefore, the electric field disappears exponentially in the liquid crystalline bulk layer. Further, the electric field includes electric field lines (electric field lines) in a direction substantially parallel to the substrate surface. That is, an in-plane electric field is generated.

  The electric field is preferably generated by an electrode pattern including any one of staggered electrodes or electrodes that generate a fringe electric field, for example, an electrode pattern including a comb-like electrode structure.

  When the liquid crystal molecules in the polarization state contained in the first subvolume and / or in the (dynamic) alignment film have a strong dielectric constant (Δε), switching occurs in addition to the coupling between the electric field and the polarization. It can have a component of dielectric coupling to the electric field, but it does not have to be.

  FIG. 1 shows an electrode pattern comprising staggered electrodes 1 and 2 applied to the inner surface of one of the substrates 3. As shown in FIG. 2, the electric field E generated by the staggered electrodes 1 and 2 is substantially localized at the substrate surface 3 that supports the electrodes 1 and 2. The electric field (E) mainly includes electric field lines in a direction substantially parallel to the substrate surface 3 on which the electrodes 1 and 2 are applied. However, the electric field (E) is not parallel to the substrate surface 3 on which the electrodes 1 and 2 are applied, but also includes some electric field lines in a direction including a direction substantially perpendicular to this surface. The direction of the electric field line changes alternately as it moves from one electrode gap to the next. Thus, the electric field is non-uniform with respect to the direction of the electric field lines (and the strength of the electric field).

  As can be appreciated by one skilled in the art, an electrode pattern that includes staggered electrodes can also include many other structures besides those shown in FIG. A common feature for all electrode patterns, including staggered electrodes, is that the electrodes are arranged in the same geometric plane.

FIG. 3 shows an electrode pattern including a comb-like electrode structure. The electrode pattern includes a first conductive layer 4 (also referred to as a common electrode or a bottom electrode), for example a layer of indium tin oxide (ITO) disposed on the substrate surface 5, and the first conductive layer A normal SiO _x insulating layer 6 disposed on top and a second conductive layer 7 (also referred to as a top electrode), for example an indium tin oxide layer disposed on top of the insulating layer, The two conductive layers 7 have a shape similar to a comb-like comb. In FIG. 3, the alignment film 8 is also shown. The electric field (fringe field) generated by this electrode structure is substantially localized near the substrate surface 5 that supports the electrodes 4 and 7. The electric field (E) comprises both electric field lines (ie fringe electric fields) (both in a direction essentially parallel to the substrate surface 5 on which the electrodes 4 and 7 are applied (E _X ) and in a direction perpendicular to it (E _z )). Includes an electric field component along the substrate surface 5 and an electric field component perpendicular to the substrate surface 5). The distribution of field lines and field strengths depends on the geometry of the electrodes 4 and 7 and their mutual position.

  Another type of fringe field generating electrode pattern is disposed on a first conductive layer (bottom electrode) disposed on a substrate surface, an insulating layer disposed on the first conductive layer, and a top of the insulating layer. And a second conductive layer (top electrode) having an opening. The second conductive layer may have a structure as shown in FIG. 56 or a similar structure. 56a shows a top electrode structure with hexagonal shaped openings, FIG. 56b shows a top electrode structure with circular spot shaped openings, and FIG. 56c shows a top with square shaped openings. An electrode structure is shown. As will be appreciated by those skilled in the art, the top electrode can have many other shapes besides those shown in FIG. This type of electrode pattern is advantageous for displaying images with a wide viewing angle. The electric field obtained by the electrode pattern according to any of the embodiments in FIG. 56 has a plurality of axes of symmetry extending along a normal to the substrate surface and passing through the center of the opening. Due to the local symmetry of the electric field, and thus the local symmetry of the liquid crystal alignment, devices with such electrode patterns have a wider viewing angle and the viewing angle is independent of direction.

  57 and 58 show one substrate of a liquid crystal device including an alignment film (not shown) that promotes homeotropic alignment, a nematic liquid crystal bulk layer 62 that exhibits positive dielectric anisotropy, and a fringe electric field generating electrode pattern. The direction of the liquid crystal bulk molecules 62 in the electric field off state and electric field on state on the surface 63 is shown, respectively, and the fringe electric field generating electrode pattern is arranged on the bottom electrode 64 arranged on the substrate surface 63 and the bottom electrode. And an insulating layer 64 and a top electrode 66 having a circular spot-shaped opening.

  The device structure of FIGS. 57 and 58 will also work with a nematic liquid crystal bulk layer that exhibits negative dielectric anisotropy.

  FIG. 59a shows a device using the comb-like electrode structure of FIG. 38, which is a side view showing the homeotropic orientation of liquid crystal bulk molecules.

  FIG. 59b shows a side view of the electrode structure in FIGS. 38 and 58 which also shows a non-uniform electric field distribution of the lines of electric force in the electric field on state.

  FIG. 59a shows a device that includes an electrode structure formed on the inner surface of a substrate (68). The molecules of the liquid crystal bulk layer are aligned perpendicular to the substrate surface by the alignment films (70) and (68) deposited on the substrates (63) and (69). The electrode structure generates an inhomogeneous electric field (fringe field) (FIG. 59b). When an electric field is applied to the cell, the molecules in the liquid crystal bulk have the property of aligning along the electric field lines when the liquid crystal material has a positive dielectric anisotropy (Δε> 0). However, this results in periodic oblique and flexural elastic deformation in the sub-volume near the electrode pattern, which in turn is a flexoelectric polarization if the liquid crystal bulk material has flexoelectric polarizability. Give rise to If the applied electric field is of an appropriate shape and of the appropriate polarity, the coupling between the electric field and the flexoelectric polarization can shorten the cell switching time.

  The device shown in FIG. 59a will also work with a nematic liquid crystal bulk layer having a negative dielectric anisotropy Δε <0.

  FIG. 60 shows the orientation of liquid crystal bulk molecules in an electric field on state in a double-sided device.

It should be understood that the device according to the invention may be single-sided or double-sided.
In one-sided embodiments according to the present invention, only one of the substrates has an electrode pattern applied to its inner surface.

  In a double-sided embodiment of the device according to the invention, both substrates comprise an electrode pattern applied to each of its inner surfaces. Therefore, in such a device, the second electrode pattern is applied to the inner surface of the other substrate so as to generate a non-uniform electric field for the second subvolume of the bulk layer adjacent to the second electrode pattern, Alternatively, the second alignment film is applied to the inner surface of the other substrate, and in this case, the electric field is not uniform in the direction of the lines of electric force and the intensity thereof.

  In a device according to the invention (both embodiments) comprising electrodes of the same type staggered on both substrates, the orientation of the electrode applied to the substrate along the first substrate surface is applied to the second substrate. It is particularly preferable to make an angle with the direction of the electrode along the surface of the second substrate. This type of arrangement substantially increases the viewing angle of the device.

  In a device according to the invention comprising staggered electrodes of the type as shown in FIG. 1 applied to both substrates, basically with respect to the direction of the electrodes disposed along the second substrate surface. It is particularly advantageous to arrange the electrodes on the first substrate surface along the substrate surface in a vertical direction.

  Furthermore, in the double-sided embodiment of the device according to the present invention, each sub-volume part (first and second sub-volume part) adjacent to the electrode pattern and / or each alignment film applied to the electrode pattern is applied. It is preferable to include a liquid crystal in a polarized state that exhibits ferroelectric coupling or flexoelectric coupling with an electric field. In this case, each of the sub-volumes and / or alignment films is stronger than a similar liquid crystal polarization that can occur in the bulk layers outside the sub-volumes and / or alignment films. However, it should be understood that the polarization intensities in the subvolume and / or alignment film may be different from each other.

  More specifically, the liquid crystal in the polarization state included in the sub-volume part and / or the alignment film exhibits either spontaneous polarization including spontaneous induction polarization or induced polarization.

  In particular, the coupling between the polarization in the subvolume and / or the alignment layer and the applied electric field is either ferroelectric, antiferroelectric, paraelectric, or flexoelectric coupling. .

In a first group of embodiments of the present invention, the alignment film includes a chiral smectic (Sm ^* ) liquid crystal material such as SmC ^* , SmC _A ^*, or SmA ^* .

A smectic liquid crystalline structure includes liquid crystal molecules disposed in adjacent smectic layers. The smectic A and smectic C phases are the two most important representatives of these “layered” liquid crystals. Furthermore, the smectic liquid crystal molecule may be achiral (eg SmA, SmC or SmC _A ) or chiral (eg SmA ^* , SmC ^* or SmC _A ^* ), in which case the term chiral means that there is no mirror symmetry.

A tilted chiral smectic liquid crystal has an inducing layer that rotates within a cone as it travels from one smectic layer to the next. The apex angle θ = 2β of this cone may generally be on the order of 45 °. Thus, a helical texture is formed that traverses the layer with a helical axis that is perpendicular to the smectic layer and parallel to the axis of the cone. However, the local spontaneous polarization (P _S ) that couples to the inductive layer also rotates helically with the same period or pitch. Such a helical structure of local polarization means that the local polarization can be eliminated by itself, that is, the bulk liquid crystal does not cause macroscopic polarization.
In the smectic A phase structure, the average direction of the molecules is perpendicular to the normal of the smectic layer (β = 0 °). That is, the molecules are directed along the normal of the smectic layer. When an electric field is applied to the chiral smectic A (SmA ^* ) liquid crystalline structure, the response to the applied electric field is a so-called paraelectric response.

  In a smectic C phase structure, the molecules are tilted at an angle β (generally on the order of 22.5 °) with respect to the normal of the smectic layer.

In a synclinic smectic, eg smectic C liquid crystalline structure, the molecules of two adjacent smectic layers are tilted in the same direction with respect to the normal of the smectic layer. When an electric field is applied to a syclinic chiral smectic, for example, a smectic C ^* (SmC ^* ) liquid crystal structure, the response to the applied electric field is a so-called ferroelectric response.

In an anticlinic smectic (eg, smectic C _A ) liquid crystalline structure, the molecules of two adjacent smectic layers tilt in opposite directions with respect to the smectic layer normal. When an electric field is applied to an anticlinic chiral smectic (eg, smectic C _A (SmC _A ^* )) liquid crystalline structure, a so-called antiferroelectric response occurs. However, if the applied electric field is higher than a predetermined threshold, the anticlinic structure changes to a sink clinic structure. That is, a ferroelectric response occurs with respect to the applied electric field.

  Thus, in this first group of embodiments of the device according to the invention, the coupling between the polarization in the alignment film and the applied electric field can be ferroelectric, antiferroelectric, or paraelectric, More preferably, it is ferroelectric. As described in the introduction part, the primary switching of molecules in the chiral smectic alignment film results in the switching of the orientation of the liquid crystal molecules in the bulk layer via elastic force (steric coupling).

Chiral smectic alignment films in this group of embodiments of the device according to the invention are synchronic chiral smectics, for example smectic C (SmC ^* ) liquid crystalline materials, in particular synchronic chiral also called ferroelectric liquid crystalline polymers (FLCP). Includes smectic C (SmC ^* ) liquid crystalline polymer.

  The chiral smectic liquid crystal material (for example, FLCP) of the alignment film is preferably insoluble in the liquid crystal material of the bulk layer. In particular, the liquid crystalline material of the alignment layer should not affect the physical properties of the liquid crystalline material of the bulk layer. Conversely, the liquid crystalline material of the bulk layer affects the physical properties of the liquid crystalline material of the alignment layer. Do not give.

  In this first group of embodiments, the bulk layer preferably comprises a chiral or achiral nematic or smectic liquid crystalline material and is nematic with zero or very small positive or negative dielectric anisotropy, ie Δε≈0. Or it is more preferable that it is a smectic liquid crystalline material. Therefore, the liquid crystalline material basically does not show dielectric coupling with the applied electric field.

  When the bulk layer contains an achiral smectic liquid crystalline material, it is appropriate that the smectic layer of the bulk layer is substantially parallel to the smectic layer of the alignment film.

  Furthermore, it is desirable that the smectic layer of the alignment film is basically oriented parallel to the applied electric field.

  The alignment films disclosed above in this first group of embodiments of the present invention can be referred to as dynamic alignment films because they are affected by and coupled to the applied electric field.

  In addition to the above, the device according to the first group of embodiments of the present invention includes a passive alignment film having the dynamic alignment film as a lower layer, and thus can provide a preferable alignment direction with respect to the dynamic alignment film.

  As described in Examples 3 and 4, alignment films comprising a chiral smectic liquid crystalline material, such as FLCP, induce flexoelectric bulk polarization in the device according to the invention.

  Further, in this group of embodiments, the liquid crystal bulk molecules adjacent to the substrate surface supporting the electrode pattern on which the alignment film is applied are larger in molecular pretilt angle than the liquid crystal bulk molecules adjacent to the opposite substrate surface. It has proven advantageous to have

  See International Patent Application No. WO 00/03288 (Patent Document 4) for further information regarding the method of manufacturing the alignment film disclosed above that exhibits spontaneous polarization.

  In a second group of embodiments of the invention, the resulting chiral dopant permanently deposited on at least one surface in the first subvolume is non-uniformly distributed in the liquid crystal bulk layer, whereby the first A direction that induces a local increase in one or more chirality related physical properties (also referred to herein as chirality effects) within the sub-volume, which is maximized at the surface and away from the surface The chiral dopant is soluble in the liquid crystal bulk layer, causing spontaneous polarization with a non-uniform distribution that decreases to

  As used herein, the term “soluble” means that the dopant can be dissolved in the liquid crystal bulk layer.

  The induced increase in the chiral effect does not occur in the entire volume of the bulk layer, but only in a limited region (subregion) of the bulk layer close to the surface.

  In this second group of embodiments, the bulk layer comprises an achiral or chiral nematic or smectic liquid crystalline material, preferably an achiral smectic (eg SmC) liquid crystalline material, and more preferably zero or very small positive or negative dielectric. An achiral smectic (eg, SmC) liquid crystalline material having anisotropy (ie, Δε≈0) can be included.

  As an example of the description of this group of embodiments, the bulk layer may comprise an achiral smectic C liquid crystal material. In the sub-region, the chiral smectic C is doped with a chiral dopant soluble in the chiral smectic C and permanently attached to the surface in the sub-volume. This dopant induces chirality, and thus induces an increase in the chirality effect in the liquid crystal bulk material in the subvolume. This induced chirality then causes spontaneous polarization in the subvolume and imparts ferroelectric properties. The actual volume of the doped subregion may be slightly different from the subvolume that exhibits chirality and produces spontaneous polarization. This is because the dopant molecule induces chirality at a predetermined distance from the dopant. By applying the electric field to the subvolume so as to show the induced spontaneous polarization, the molecules are switched very fast due to direct ferroelectric coupling with the applied electric field. This fast ferroelectric switching then results in fast switching of the bulk molecules outside the subvolume due to the elastic coupling between the molecules in the surface subregion and the neighboring molecules in the bulk volume.

  The chiral dopant is permanently attached to the surface. This should be interpreted as being bound to the surface so that the dopant is prevented from moving freely within the bulk volume. Although dopants are permanently attached to the surface, these dopants can exhibit limited mobility. In particular, it can exhibit mobility such that the dopant molecules can reorient at the surface during switching due to an applied external electric field, for example.

  The surface to which the dopant is deposited should be considered not only to include or define the boundary of the bulk layer, but also to include the surface or plane located within the subvolume. Thus, in this context, the term “surface” includes any physical or geometric surface or plane that contacts the bulk layer material in the subvolume, either directly or indirectly through a dopant material. Means you can.

  The dopant is preferably attached to the surface of the electrode pattern or the alignment film that is arranged to interact with the liquid crystal in the bulk layer and thus provide the preferred molecular orientation of the liquid crystal material.

  In this second group of embodiments of the device according to the invention, the coupling between the polarization in the first subvolume and the applied electric field is ferroelectric, anti-reflective, as can be seen from the above description. It can be ferroelectric or paraelectric, and is more preferably ferroelectric.

  For further information on the previously disclosed methods for producing subvolumes exhibiting induced spontaneous polarization, see International Patent Application No. WO2003 / 081326 (Patent Document 5).

  In a third group of embodiments of the device according to the invention, the polarization of the liquid crystal in the first subvolume is induced by the oblique and / or bending deformation of the liquid crystal in the subvolume, whereby the first subvolume. A flexoelectric coupling occurs between the liquid crystal in a polarized state in the volume and the electric field.

は、それぞれ斜向変形および屈曲弾性変形である。一般に、弾性変形がより強くなればなるほどＰ_{ｆｌｅｘｏ}も大きくなる。フレクソエレクトリックは液晶のユニバーサルな物理的性質であるが、異なる符号のＰ_{ｆｌｅｘｏ}を示す、そしてゼロのＰ_{ｆｌｅｘｏ}を有するような液晶材料も存在する。 The flexoelectric effect in liquid crystals is similar to the piezoelectric effect in solid materials, but its properties are quite different. By flexoelectric is meant the polarization of the liquid crystal material that occurs as a result of elastic deformation, for example bending and / or oblique deformation. In addition to the permanent pure dipole moment, this flexoelectric is noticeable for liquid crystal materials consisting of molecules that also have “shape polarity”. All flexoelectric polarization _{P flexo is} shown by _{P flexo = e s S + e} b B, where, _{e s} is the diagonal flexoelectric coefficients, _{e b} is bent flexoelectric coefficients. These coefficients are extremely important parameters that determine the strength of flexoelectric polarization.

Are oblique deformation and bending elastic deformation, respectively. In general, the stronger the elastic deformation, the greater the P _flexo . Although flexoelectric is a universal physical properties of the liquid crystal shows a P _flexo different codes, and there is also a liquid crystal material having a zero P _flexo.

  As known to those skilled in the art, liquid crystalline materials that produce oblique and / or bending deformations can induce polarization that causes flexoelectric coupling (flexoelectric effect) to an applied electric field.

In this third group of embodiments of the device according to the invention it is preferred to use a liquid crystalline material having a high flexoelectric polarizability, ie a liquid crystalline material exhibiting a high flexoelectric polarization under elastic deformation. Liquid crystalline material generally such has at least one high value of the flexoelectric coefficients e _s and e _b. It should be understood that liquid crystalline materials for use in this third embodiment of the device cannot be arbitrarily selected, as there are liquid crystalline materials that do not exhibit flexoelectric polarization even under elastic deformation.

In general, there are oblique deformation, bending deformation and asymmetric combined (oblique + bending) deformation.
In order to obtain the desired effect according to the present invention, the flexoelectric effect in the first sub-volume is determined by any occurrence of the bulk layer outside the sub-volume (first sub-volume and second sub-volume). It is important to be more powerful than the flexoelectric effect you get.

  For example, this effect may be achieved by applying a matching layer with varying anchoring properties on one or both of the substrate surfaces, e.g., affecting the orientation direction and / or protrusions extending into the subvolume. It can be obtained by causing deformation and / or bending deformation. The surface topology resulting from the protrusions, alone or in combination with changing anchor properties, gives rise to flexoelectric polarization of adjacent liquid crystals.

  In such a single-sided embodiment, it is desirable to apply an additional (second) alignment film that exhibits a predetermined alignment direction, such as planar or homeotropic, on the inner surface of the other substrate.

  By applying a suitable surface treatment for confining the surface of the solid substrate, for example, by applying a so-called (surface-induced) alignment layer on the surface of the confinement substrate facing the liquid crystal bulk, the desired initial alignment of the liquid crystal layer is generally achieved without an electric field Can be obtained. This initial liquid crystal alignment is determined by the interaction between the solid surface and the liquid crystal. Since the orientation of the liquid crystal molecules adjacent to the confining surface is transmitted to the liquid crystal molecules in the bulk via an elastic force, basically the same orientation can be imposed on all the liquid crystal bulk molecules. The inducing layer of liquid crystal molecules near the confining substrate surface is oriented in a predetermined direction, for example, a direction perpendicular to the confining substrate surface (also referred to as homeotropic direction or vertical direction) or parallel to the confining substrate surface (also referred to as planar direction). Limited to In some cases, it may be advantageous to further direct the liquid crystal bulk molecules to a predetermined tilt angle (pretilt angle) relative to the substrate.

  In this third group of embodiments of the invention, a dopant that promotes flexoelectric polarization is permanently attached to at least one surface in the first subvolume, thereby in the first subvolume. In the bulk layer as a result of the occurrence of flexoelectric polarization that has a non-uniform distribution that promotes a local increase in one or more physical properties of and increases at a maximum and decreases away from the surface. It can be distributed unevenly and the dopant is soluble in the liquid crystal bulk layer.

  Dopants that can be used to promote ferroelectric polarization in the subvolume are, for example, banana-shaped, drop-shaped, drop-banana composite shaped dopants, and two or more thereof having desirable effects due to anisotropic shapes A dopant selected from the group consisting of: It is known to those skilled in the art that such dopants provide higher flexoelectric coefficients. Such a dopant may be a mesogenic compound, but is not limited thereto.

  An example of a method for producing homeotropic alignment involves coating the confined substrate surface with a surfactant, such as a surfactant such as lecithin or hexadecyltrimethylammonium bromide. Next, it is also preferable to rub the coated substrate surface in a predetermined direction so that the planar alignment of the liquid crystal molecules induced by the electric field is in a predetermined rubbing direction.

  As an example of a method for causing the planar alignment, there can be mentioned a so-called organic film rubbing method in which, for example, a polyimide organic film is applied to the substrate surface. Thereafter, the organic film is rubbed in a predetermined direction using a cloth so that liquid crystal molecules in contact with the film are oriented in the rubbing direction.

  4-19 are adjacent to the substrate surface supporting the electrode pattern (this electrode pattern is not shown in the figure) as described above due to the surface topology of the alignment film and / or anchor properties (including the alignment direction). It illustrates how the flexoelectric polarization can be induced within the subvolume. The direction of flexoelectric polarization is indicated by an arrow in the figure, and the dotted line indicates the alignment direction of the liquid crystal molecules.

  4-17 illustrate flexoelectric polarization induced by alignment films that exhibit pyramidal or rectangular surface geometries and different types of alignment directions, such as homeotropic and planar alignment. A method for forming this type of periodic surface topology is described by D. Flanders, D. Shaver and H. Smith, Applied Physics Letters, 55, 2506 (1978); G Boyd, Applied Physics Letters, 35, 444 (1979); GP Brian-Brown, C V Brown, I C Sage and V C Hull, Nature, V392. 365 (1998) (Non-Patent Document 5); and C Brown, M Toller, V Huy and G. Bryan-Brown, Liquid Crystals, 27, 233 (2000) (Non-Patent Document 6). It is disclosed.

  4, 7 and 8 each show an alignment film having a pyramidal geometry (applied to the pyramidal protrusions) and a homeotropic alignment. In FIG. 4, the substrate surface within and between the pyramid protrusions also exhibits homeotropic orientation. The opposite substrate surface includes an additional alignment film that exhibits planar alignment.

  FIG. 5 shows an alignment film having a pyramidal geometry with homeotropic alignment (applied to the pyramidal protrusions) and planar alignment within and between the pyramidal protrusions.

  6, 13 and 14 each show an alignment film having a pyramidal geometry (applied to the pyramidal protrusions) and a planar alignment. In FIG. 6, the substrate surface within and between the pyramid protrusions also exhibits a planar orientation. The opposite substrate surface includes an additional alignment film that exhibits planar alignment.

  FIG. 9 shows an alignment film having a pyramidal geometry (applied to the pyramidal protrusions) and a planar alignment. The opposite substrate surface includes an additional alignment film that exhibits homeotropic alignment.

  FIG. 10 shows an alignment film having a pyramidal geometry (applied to an asymmetric pyramidal protrusion) and a planar alignment. The opposite substrate surface includes an additional alignment film that exhibits homeotropic alignment.

  FIG. 11 shows an alignment film having a pyramidal geometry with planar alignment (applied to the pyramidal protrusions) and homeotropic alignment in and between the pyramidal protrusions.

  FIG. 12 shows an alignment film having a pyramidal geometry in which planar and homeotropic alignments (applied to pyramidal protrusions) are alternately arranged. The opposite substrate surface includes an additional alignment film that exhibits planar alignment.

  FIG. 15 is a double-sided embodiment in which the single-sided embodiment shown in FIG. 4 is provided on both sides, with flexoelectric polarization localized on the inner surface of each of the substrates.

  FIG. 16 shows an alignment film having a rectangular geometry in which the planar and homeotropic alignments (applied to the rectangular protrusions) are alternately arranged.

  FIG. 17 shows an alignment film having a rectangular geometry with planar alignment (applied to a rectangular protrusion).

  18 and 19 are schematic cross-sectional views of a device according to the present invention in which flexoelectric polarization is generated by a polymer wall that divides the device gap in a number of cells. A method for producing this type of polymer wall is described by R Caputo, L Dosio, AV Schaff, A Wertri and C Umeton, Optics Letters, 29, 1261 (2004) (Non-Patent Document 7); And G Strangi, V Verna, R Caputo, A Dolka, C Versace, N Skalazza, C Umeton, and R ing.

  Unlike the above method, oblique and / or bending deformations can also be performed in the entire bulk (ie bulk polarization) in the device according to the invention.

Thus, the device according to the invention can comprise a bulk layer having an asymmetric oblique-bending composite deformation, in which:
The first sub-volume liquid crystal substantially shows the bend deformation of the bending flexoelectric coefficients e _b are the primary flexoelectric coefficients flexoelectric polarization (ie _{| e b |> | e s} | a (In such a case, it is preferable that the liquid crystal of the first sub-volume portion a has negative dielectric anisotropy (Δε ≦ 0), and the first sub-volume portion contains liquid crystal substantially showing bending deformation. ) Or the liquid crystal of the first sub-volume substantially exhibits oblique deformation, and the oblique flexoelectric coefficient _es is the main flexoelectric coefficient of the flexoelectric deformation (i.e., | _es | | e b _| a is) (liquid crystal bulk layer in such a case, positive dielectric indicates anisotropy ([Delta] [epsilon] ≧ 0), the first sub-volume is to include a liquid crystal exhibiting substantially the diagonal deformation Preferred )

  In these cases, the flexoelectric effect in the first sub-volume section is stronger than the flexoelectric effect of the bulk layer outside the first sub-volume section.

In an embodiment of the third group of devices according to the present invention, the liquid crystal of the oblique flexoelectric coefficients e _s has become a major flexoelectric coefficients flexoelectric polarization (typically bulk layer is positive It is also possible to use a bulk layer with oblique deformation that exhibits dielectric anisotropy (Δε ≧ 0). In this case, the electrode pattern according to the present invention is appropriately applied on both sides of the substrate, and a non-uniform electric field is applied across each strongly sub-volume of the bulk layer adjacent to the electrode pattern.

Similarly, unlike the embodiment, showing a negative dielectric anisotropy liquid crystal bulk layer in the bending flexoelectric coefficients e _b is a major flexoelectric coefficients flexoelectric polarization (typically (Δε ≦ 0)) Bending deformation can also be exhibited by the bulk layer of the device according to this third group of embodiments. In this case, electrode patterns are appropriately applied on both sides of the substrate.

  When a device according to the invention as described above comprises a bulk layer having a symmetrical oblique or bending deformation and an electrode applied only on one side of the substrate (single-sided embodiment), the flex in the first subvolume The xoelectric polarization has an intensity equal to that of the flexoelectric polarization in the second subvolume adjacent to the inner surface of the substrate that does not have an electrode pattern but has an alignment film on the top.

  In this third group of embodiments, the bulk layer preferably comprises a nematic (chiral or achiral) liquid crystalline material. Furthermore, when the bulk layer liquid crystalline material is deformed by elastic deformation, it is appropriate for this material to exhibit significant flexoelectric polarization. Therefore, it is desirable that the liquid crystal material of the bulk layer exhibits flexoelectric polarization.

  The strength of flexoelectric polarization is determined not only by the magnitude and sign of the flexoelectric coefficient, but also by the degree of elastic deformation, for example, the flexoelectric polarization increases as the cell gap in a liquid crystal device becomes narrower. Should.

  Furthermore, in this third group of embodiments, the average direction of flexoelectric polarization in the electric field off state in the first sub-volume is parallel to the substrate on which the electrode pattern is applied or 90 In-plane switching of the liquid crystal in the bulk layer is achieved when tilted at an angle smaller than °, preferably essentially when orthogonal to the direction in which the in-plane electric field is to be generated.

The invention further relates to a method for manufacturing the liquid crystal device according to the invention. This method
Applying an electrode pattern to an inner surface of a substrate, the electrode pattern being capable of generating a non-uniform electric field across a first subvolume of a liquid crystal bulk layer adjacent to the electrode pattern, the electric field being Steps that are not uniform with respect to the direction of
Applying an alignment film to the electrode pattern, and generating the electric field beyond the alignment film;
Forming a cell gap between the electrode substrate having the electrode pattern and an alignment film applied thereon and a second substrate;
Filling the cell gap with a liquid crystalline material forming a liquid crystal bulk layer, and supplying a liquid crystal in a polarized state into the first sub-volume and / or into the alignment film, the polarization comprising: A bulk layer adjacent to the first sub-volume, the exterior of the alignment film and / or the inner surface of the second substrate, the second alignment film or an optional second electrode pattern applied to the second alignment film; It is stronger than any possible similar liquid crystal polarization of the bulk layer outside the second sub-volume, and performs the switching of the liquid crystal in combination with the electric field, and the switching of the liquid crystal in the bulk layer through the elastic force. Can be achieved.

  In summary, the present invention relates to a non-uniform in-plane electric field generated by the electrode pattern over the first subvolume of the bulk layer adjacent to the electrode pattern and within the first subvolume and / or the electrode pattern. Relating to a liquid crystal device driven at least in part by linear coupling, for example ferroelectric coupling and / or flexoelectric coupling, with a liquid crystal in a polarized state contained in an alignment film applied to (Ii) the first sub-volume, the outside of the alignment film, and (ii) the inner surface of the other substrate or the second alignment film or an optional second electrode pattern applied to the second alignment film. More powerful than any possible similar liquid crystal polarization of the bulk layer outside the second subvolume of the adjacent bulk layer.

From the previous description of the liquid crystal device according to the present invention, other preferred features of the above method will be understood.
The invention will now be illustrated by the following non-limiting examples.

Example 1:
A cell comprising a bulk layer with composite orientation (HAN) and staggered electrodes

  A sandwich cell (FIG. 20) comprising two parallel glass substrates 9 and 10 forming a cell gap of about 2 μm was used. The electrode patterns 11 arranged alternately (shown in FIG. 1) were provided on one inner surface of the substrate 9. The distance between adjacent electrodes was about 20 μm.

  A first alignment film 12 made of Nissan SE-2170 is deposited on the electrode pattern 11, and the first alignment film is promoted to promote uniform planar alignment of the liquid crystal bulk layer including the liquid crystal molecules 13 provided in the cell gap. 12 was rubbed in parallel to the electrode pattern 11.

  A second alignment film 14 made of Nissan SE-1211 that promotes homeotropic alignment was deposited on the inner surface of the other substrate 10.

  The cell gap was filled with a nematic liquid crystalline material MLC 16000-000 (supplied by Merck) having a positive dielectric anisotropy (Δε> 0).

Due to the orientation of the alignment films 12 and 14, the nematic bulk 13 is in a composite alignment (HAN) state. That is, the orientation of the substrate 9 supporting the electrode pattern 11 is planar, but the other substrate 10 is homeotropic (FIGS. 20 and 21). Such elastic deformation of the nematic bulk layer 13 causes flexoelectric polarization (P _flexo ). 21 to 23 indicate the direction of the optical axis of the sample.

  Since the oblique deformation is localized on the substrate 9 supporting the electrode pattern 11 and the MLC 16000-000 exhibits positive dielectric anisotropy, the place where the oblique deformation is dominant, that is, the substrate supporting the electrode 11. 9, the most powerful flexoelectric polarization is localized (FIG. 20).

Elastic deformation and flexoelectric polarization are parallel to the electrode pattern 11 and exist in the same plane perpendicular to the cell substrates 9 and 10. The flexoelectric polarization is linearly coupled to the applied electric field E and performs high-speed switching of the liquid crystal 13. The total switching time τ _rise + τ _fall measured was about 8-12 ms with an applied voltage of 25V. In a conventional IPS liquid crystal device, the total switching time under the same conditions is about 28-34 ms.

  22 and 23 schematically show the switching of the nematic liquid crystal 13 in a single electrode gap, respectively. As can be seen from these two figures, the direction of switching is determined by the polarity of the electric field E. Nematic LC molecules 13 in two adjacent electrode gaps switch in a clockwise and counterclockwise direction as shown in FIGS. 24 and 25, respectively. These figures show two states of the cell corresponding to different field polarities of the applied electric field (E). This cell was seen between crossed polarizers with a λ-red optical plate inserted between them. Different colors correspond to different positions of the guiding layer n (indicated by arrows in FIGS. 24 and 25) relative to the optical axis of the λ-red optical plate.

Example 2:
A cell comprising a bulk layer with composite orientation (HAN) and staggered electrodes

  In this example, the same type of sandwich cell as in Example 1 was used, but the HAN texture was inverted (FIG. 26). Therefore, as shown in FIGS. 26 and 27, in the substrate 15 supporting the electrode pattern 17, the orientation induced by the first alignment film 18 is homeotropic, and in the opposite substrate 16, the second alignment film 20 The induced orientation was planar.

  In addition, the cell gap was filled with another nematic liquid crystalline material 19, MDA-05-187 (supplied by Merck) having negative dielectric anisotropy (Δε <0).

The oblique deformation is localized on the substrate 15 that supports the electrode pattern 17 and MDA-05-187 exhibits negative dielectric anisotropy, so that the bending deformation is dominant, that is, the electrode 17 is supported. The most powerful flexoelectric polarization (P _flexo ) is localized on the substrate 15 (FIG. 26). The double-sided arrows in FIGS. 27 to 29 indicate the direction of the sample optical axis.

Nematic switching (including switching time) has been found to be similar to the switching described in Example 1, and this switching is shown schematically in FIGS. However, unlike the switching described in Example 1 in which the flexoelectric coupling (P _flexo ) and the dielectric coupling are in the same direction, in this example, these couplings are in opposite directions. In a weak or moderate electric field, this flexoelectric coupling (P _flexo ) dominates the dielectric coupling between the electric field (E) and the dielectric anisotropy. However, dielectric coupling is dominant at strong electric fields (E) and high frequencies. Therefore, by first applying a dc voltage to the electrodes, nematic molecules 19 cause clockwise and counterclockwise directions for flexoelectric coupling, depending on the polarity of the applied electric field (E) in the corresponding electrode gap. To switch respectively. A strong radio frequency pulse causes the nematic molecule 19 to switch back due to dielectric coupling. Therefore, by applying a DC voltage, the nematic molecule 19 is switched to the on state (FIGS. 30a, 30b and 30c), while the high frequency pulse causes the nematic molecule 19 to be parallel to the electrode 17 as in Example 1 (FIG. 31a and 31b), switching the nematic molecule 19 back to the preferred direction of the initial electric field off of the orientation (indicated by the double-headed arrows in FIGS. 30 and 31).

Example 3:
Cell containing chiral smectic alignment film and staggered electrodes The cell used in this example (FIG. 32) had the same structure as that used in Example 1. However, in this embodiment, an alignment film (not shown) including NISSE-2170 rubbed in a single direction along the electrode 23 to promote quasi-planar alignment having _a pretilt angle θa is used. Both inner surfaces were coated.

On the top of the alignment film covering the electrode pattern 23, a thin film (not shown) of ferroelectric liquid crystal polymer (FLCP), more specifically, a strong dielectric side chain polysiloxane was deposited. The FLCP layer has a molecular tilt angle theta _b, was oriented on the geometry, such as bookshelf. That is, it was in an oriented state with the smectic layer perpendicular to the substrate surface 21.

  The cell gap was filled with an in-house prepared nematic liquid crystalline material 24 having negative dielectric anisotropy (Δε <0) and immiscible (insoluble) in FLCP.

  The applied electric field (E) in this embodiment does not switch nematic molecules 24 directly due to negative dielectric anisotropy. However, the electric field E switches the molecules of the FLCP due to the spontaneous polarization of the FLCP material, which in turn switches the nematic liquid crystalline molecules 24 of the bulk layer via elastic forces (International Patent Application No. WO 00 / 03288 (Patent Document 4)). Therefore, by changing the polarity (E) of the electric field, the preferred direction of orientation of the nematic bulk 24 is switched in the plane of the substrates 21 and 22 (ie, in-plane switching).

As can be seen from FIG. 32, in one electric field characteristic (E), the molecular pretilt angle has a uniform distribution over the nematic bulk 24, but in the other electric field polarity (E), the nematic bulk 24 causes oblique deformation. This deformation causes flexoelectric polarization (P _flexo ) as shown in FIG. However, like the spontaneous polarization (P _s ) of the FLCP layer, the flexoelectric polarization (P _flexo ) is linearly coupled to the electric field (E) and causes in-plane switching.

Similar to Examples 1 and 2, it was found that the total switching time (τ _rise + τ _fall ) was about 8 to 12 ms at an applied voltage of 25V.

Pretilt angle theta _a in no substrate 22 of the electrode 23 is smaller than the pretilt angle theta _b in the electrode 21 that supports the electrode pattern 23, the largest flexoelectric polarization _{(P flexo)} is basically the electrode patterns 23 Is localized to the surface that supports and thus the coupling to the applied electric field (E) is stronger, allowing more efficient switching of the nematic bulk 24 (ie shorter switching time).

Example 4:
A cell comprising a chiral smectic alignment film and staggered electrodes

  The cell used in this example (FIG. 34) had the same structure as that used in Example 3. However, in this example, both the substrates 25 and 26 are alignment films (26) rubbed in a single direction along the electrode pattern 27 to promote quasi-homeotropic alignment with a pretilt angle (θ) of less than 90 °. The inner surface of was coated (FIG. 34). Further, an FLCP layer (not shown) was aligned with a smectic layer parallel to the substrate 25.

As can be seen from FIG. 34, in one electric field polarity (E), the molecular pretilt angle has a uniform distribution over the nematic bulk 28, but in the other electric field polarity (E), the nematic bulk 28 undergoes bending deformation, and this deformation is _{Flexoelectric} polarization (P _flexo ) as shown in FIG. 35 is generated. This polarization (P _flexo ) is linearly coupled to the electric field (E) and causes in-plane switching.

  FIGS. 36a and 36b schematically show the switching of the FLCP layer.

  The switching of the nematic bulk 28 (including the switching time) was found to be the same as the switching described in Example 3.

Example 5:
A cell comprising a bulk layer having composite orientation (HAN) and a comb-like electrode for generating a fringe electric field

  In this example, a sandwich cell with two parallel glass substrates 29 and 30 forming a cell gap of about 2 μm was used (FIG. 37). An electrode pattern including a first conductive layer 31, an insulating layer 32 having a thickness of about 300 nm, and a comb-shaped second conductive layer 33 is provided on the inner surface of one of the substrates 29 (one side) Device) (FIG. 37). FIG. 3 shows the distribution of the fringe electric field components generated by this electrode pattern.

  As in the example, a first alignment film 34 made of Nissan SE1211 for promoting homeotropic alignment of the liquid crystal bulk layer 35 provided in the cell gap was deposited on the substrate 29 supporting the comb-like electrode 33. .

  As in the second embodiment, the second alignment film 36 made of Nissan SE2170 is deposited on the inner surface of the other substrate 30 and rubbed in parallel with the electrodes 31 and 33, and the liquid crystal bulk layer 35 provided in the cell gap. Promoted uniform planar orientation.

  As shown in FIG. 2, the cell gap was filled with nematic liquid crystalline material MDA-05-187 having negative dielectric anisotropy (Δε <0).

Therefore, the nematic liquid crystal 35 filling the cell gap has a HAN structure (FIGS. 37 and 38), and the strongest flexoelectric polarization (P _flexo ) is localized near the substrate 29 that supports the comb-like electrode 33. The double-sided arrows in FIGS. 38 to 40 indicate the direction of the optical axis of the sample.

As shown in FIGS. 39 and 40, the parallel component of the fringe electric field (E) _{causes the} flexoelectric polarization (P _flexo ) adjacent to the two parallel side surfaces of the comb-like electrode 33 to rotate in the clockwise direction in the plane, respectively. And counterclockwise to produce a substantial electro-optic response.

However, as shown in FIGS. 41 and 42, the vertical component of the fringe electric field (E) _{switches the} flexoelectric polarization (P _flexo ) in the middle between the two parallel sides of the comb electrode 33 out of plane. However, this does not cause an electro-optic response.

  The displayed image of this device was shown to have a high contrast. FIG. 43 shows the electric field on state, and FIG. 44 shows the electric field off state.

  Furthermore, the device also has a wide viewing angle for in-plane switching.

  Furthermore, in this device, the voltage required to drive the switching of the nematic bulk 35 is about 6V, which is considerably lower than the voltage required for conventional IPS displays (15-20V).

The total switching time (τ _rise + τ _fall ) of this device was found to be about 3 ms. The rise time (τ _rise ) was about 2 ms, and the fall time (τ _fall ) was about 0.9 ms. Therefore, the switching time is much shorter than that of the conventional IPS display.

Example 6:
A cell comprising a bulk layer having composite orientation (HAN) and a comb-like electrode for generating a fringe electric field

  As in Example 5, the same type of sandwich cell was used in this example, but the HAN texture was inverted. Therefore, the orientation on the substrate supporting the electrode was planar, and the orientation on the opposite substrate was homeotropic (ie similar to Example 1).

  The cell gap was further filled with another nematic liquid crystalline material, MLC 16000-000 (supplied by Merck) with positive dielectric anisotropy (Δε> 0). This material was also used in Example 1.

As in Example 1, the nematic liquid crystal has a HAN structure, and the strongest flexoelectric polarization (P _flexo ) is localized near the substrate supporting the comb-like electrode.

  Nematic material switching (including switching time) was found to be similar to the switching described in Example 5.

Example 7:
A cell comprising a chiral smectic alignment film and a comb-like electrode for generating a fringe electric field

  The cell used in this example (FIG. 45) had the same structure as that used in Example 5. However, in this example, the inner surfaces of both substrates 37 and 38 were coated with Nissan SE-2170 rubbed parallel to the comb-like electrode 41 to promote unidirectional planar alignment.

  A thin film 43 of ferroelectric liquid crystal polymer (FLCP), more specifically a strong dielectric side chain polysiloxane, was deposited on top of the alignment film covering the electrodes 41 and 42. The FLCP film 43 was in an oriented state in a geometric shape like a bookshelf. That is, it was in an oriented state with the smectic layer perpendicular to the substrate surface 37. The cell gap was filled with an in-house prepared nematic liquid crystalline material 44 having negative dielectric anisotropy (Δε <0) and immiscible (insoluble) in FLCP43.

  As in Example 3, the applied electric field (E) is caused by negative dielectric anisotropy and does not directly switch the nematic molecules 44. However, the electric field (E) switches the molecules of the FLCP 43 by spontaneous polarization of the FLCP material 43, which in turn switches the nematic liquid crystalline molecules 44 in the bulk layer via elastic forces (International Patent Application No. WO00 / 03288 (Patent Document 4)) (FIGS. 47 and 48).

  Switching of the FLCP molecule 43 by applying a fringe electric field (E) causes the electric field for the entire bulk (ie, the electric field generated between electrodes applied to the surfaces of separate substrates), as shown in FIG. It was found to be more efficient than applying. The device shown in FIG. 51 includes ITO electrodes 45 and 46 applied to substrate surfaces 47 and 48, respectively, and FLCP layers 49 and 50 applied to the ITO electrodes 45 and 46, respectively. The cell gap separated by the spacer 51 is filled with the achiral nematic liquid crystalline material 52.

  The contrast of the displayed image of the device with fringing electric field was shown to have a higher contrast than the image of the device where the electric field is generated across the entire bulk layer (FIG. 52) (see FIGS. 49 and 50). .

  In addition, the drive voltage of about 6.7V for the device with fringing electric field was significantly lower than the drive voltage of about 50V for the device in which the electric field is generated across the entire bulk layer (the volt displayed on the oscilloscope is Because of the characteristics, it must be multiplied by 10 times).

Example 8:
A cell including a chiral smectic alignment film and a comb-like electrode for generating a fringe electric field

  Example 7 is repeated, but the nematic liquid crystalline material exhibits positive dielectric anisotropy (Δε> 0).

Example 9:
A cell including a chiral smectic alignment film and a comb-like electrode for generating a fringe electric field

  Example 7 is repeated, but the FLCP layer is aligned with the smectic layer parallel to the substrate surface. 53 and 54 show the expected switching of FLCP.

Example 10:
A cell (double-sided device) comprising a chiral smectic alignment film and a comb-like electrode for generating a fringe electric field

  Example 7 is repeated, but in order to generate a fringe electric field near both substrates 53 and 54, each inner surface of substrates 53 and 54 supports the electrode patterns 55 and 56 disclosed above, respectively (double-sided device). (FIG. 55). Further, each substrate surface 53 and 54 includes passive alignment films 57 and 58, respectively, and further includes FLCP layers 59 and 60, which are deposited on the electrode patterns 55 and 56, respectively, and face the achiral nematic liquid crystalline bulk layer 61. .

Example 11:
A cell (double-sided device) comprising a chiral smectic alignment film and a comb-like electrode for generating a fringe electric field

  Example 8 is repeated, but both inner surfaces of the substrate support the electrode pattern disclosed above for generating a fringe field near both substrate surfaces (double-sided device).

Example 12:
Cell (double-sided device) comprising a chiral smectic sub-volume and a comb-like electrode for generating a fringe electric field

  Example 7 is repeated, but each inner surface of the substrate supports the electrode pattern disclosed above (double-sided device), and each substrate surface includes a passive alignment film. However, instead of covering each alignment film with the FLCP layer, a chiral molecule (chiral dopant) is attached to the alignment film. In addition, the cell gap is filled with an achiral smectic liquid crystalline material, and the chiral molecules are located in the subvolume of the achiral smectic bulk layer, and thus close to the substrate supporting the comb-like electrode. In the volume part, chirality is induced.

  Although the present invention has been described in detail with reference to specific embodiments of the present invention, those skilled in the art can perform various polarizations and modifications without departing from the spirit and scope of the invention. It will be clear.

Claims (24)

First and second confinement substrates;
A liquid crystal bulk layer disposed between the substrates;
A first electrode pattern applied to an inner surface of the first substrate;
A first alignment film disposed on the bulk surface of the bulk layer so as to interact with the bulk layer, and applied on the first electrode pattern;
The first electrode pattern is disposed to generate a non-uniform electric field with respect to the first sub-volume portion of the bulk layer adjacent to the first alignment layer, and the electric field has a direction of electric lines of force and In the liquid crystal device in which the electric field strength is not uniform and the electric field is also generated for the first alignment film,
The liquid crystal in the polarization state is further included in the first sub-volume section and / or the first alignment film, and the polarization of the liquid crystal is (i) the first sub-volume section and / or the first alignment. Any of the bulk layer outside the film, and (ii) outside the second subvolume of the bulk layer adjacent to the second substrate and / or a second alignment film disposed on the second substrate The liquid crystal in a polarized state, which is stronger than similar liquid crystal polarization that can occur and is contained in the first sub-volume and / or in the first alignment film, is at least due to the coupling between the electric field and the polarization. A liquid crystal device, wherein the liquid crystal device is partially switched, and switching of the liquid crystal of the bulk layer is achieved by elastic force.   2. The liquid crystal device according to claim 1, wherein the inner surface of the second substrate generates a non-uniform electric field for the second sub-volume of the bulk layer adjacent to the second electrode pattern. The second electrode pattern is applied to the liquid crystal device, the electric field is not uniform with respect to the direction of the lines of electric force and the strength of the electric field, and a second alignment film is applied on the second electrode pattern.   3. The liquid crystal device according to claim 1, wherein the polarization in the first sub-volume section and / or in the alignment film is caused by the bulk layer outside the first sub-volume section and / or the alignment film. A liquid crystal device that is more powerful than any possible similar liquid crystal polarization.   The device according to any one of claims 1 to 3, wherein the coupling between the liquid crystal in the polarization state and the electric field is a ferroelectric coupling, an antiferroelectric coupling, a paraelectric coupling, a flexible coupling. A liquid crystal device that is selected from the group consisting of a xoelectric bond and any combination thereof.   5. The liquid crystal device according to claim 4, wherein the coupling between the liquid crystal in a polarized state and the electric field is a ferroelectric coupling.   The liquid crystal device according to claim 5, wherein the alignment film includes a liquid crystalline material that generates spontaneous polarization. The liquid crystal device according to claim 6, wherein the alignment film includes chiral smectic C, SmC ^* , and a liquid crystalline material.   5. The liquid crystal device according to claim 4, wherein the liquid crystalline material that generates spontaneous polarization is a liquid crystalline polymer capable of ferroelectric coupling, antiferroelectric coupling, and / or paraelectric coupling with the electric field.   The liquid crystal device according to claim 5, wherein the sub-volume part includes a liquid crystalline material exhibiting induced spontaneous polarization.   10. The liquid crystal device according to claim 9, wherein a chiral dopant is distributed non-uniformly in the bulk layer as a result of being permanently attached to at least one surface in the first subvolume. Causes a local increase in one or more chiral properties related to the chirality in the first sub-volume, and produces a spontaneous polarization having a non-uniform distribution that is maximal at the surface and decreases as the distance from the surface increases. And the chiral dopant is soluble in the liquid crystal bulk layer.   5. The liquid crystal device according to claim 4, wherein the coupling between the polarized liquid crystal and the electric field is a flexoelectric coupling.   12. The liquid crystal device according to claim 11, wherein the chiral dopant is distributed non-uniformly in the bulk layer as a result of being permanently attached to at least one surface in the first subvolume. Thereby facilitating the local increase of one or more physical properties in the first sub-volume and the generation of spontaneous polarization having a non-uniform distribution that is maximized at the surface and decreases as the distance from the surface increases. The liquid crystal device, wherein the chiral dopant is soluble in the liquid crystal bulk layer.   13. The liquid crystal device according to claim 12, wherein the dopant is selected from the group consisting of banana shape, drop shape, drop-banana composite shape dopant, and any mixture of two or more thereof. LCD device.   The liquid crystal device according to claim 11, wherein the coupling between the liquid crystal in a polarized state and the electric field is a combination of a flexoelectric coupling and a dielectric coupling.   12. The liquid crystal device according to claim 11, wherein the liquid crystal bulk layer includes a nematic liquid crystalline material that generates flexoelectric polarization under elastic deformation.   16. The liquid crystal device according to claim 15, wherein the polarization of the liquid crystal in the first sub-volume section is generated by the alignment film having changed anchor characteristics and / or protrusions extending into the first sub-volume section. A liquid crystal device caused by oblique deformation and / or bending deformation within the liquid crystal device. A liquid crystal device according to claim 15, wherein the liquid crystal bulk layer showed HasuMuko-bending complex deformation, e _b is a major flexoelectric coefficients flexoelectric polarization, said first subvolume The liquid crystal is a liquid crystal device that causes bending deformation. A liquid crystal device according to claim 15, wherein the liquid crystal bulk layer results in HasuMuko-bending complex deformation, e _s is the major flexoelectric coefficients flexoelectric polarization, the said first subvolume A liquid crystal device that produces oblique deformation.   16. The liquid crystal device according to claim 15, wherein the liquid crystal bulk layer has positive dielectric anisotropy and oblique deformation, and an electrode pattern is applied to each inner surface of the substrate. A liquid crystal device adapted to generate a non-uniform electric field for each sub-volume of the bulk layer adjacent to.   16. The liquid crystal device according to claim 15, wherein the liquid crystal bulk layer has negative dielectric anisotropy and bending deformation, and an electrode pattern is applied to each inner surface of the substrate. A liquid crystal device adapted to generate a non-uniform electric field for each sub-volume of an adjacent bulk layer.   21. The liquid crystal device according to any one of claims 1 to 20, wherein the electrode pattern includes electrodes arranged alternately.   21. The liquid crystal device according to any one of claims 1 to 20, wherein the electrode pattern includes a fringe electric field generating electrode.   23. The liquid crystal device according to claim 22, wherein the electrode pattern is disposed on a first conductive layer disposed on the substrate, an insulating layer disposed on the first conductive layer, and a top portion of the insulating layer. And a second conductive layer, wherein the second conductive layer has a comb-like shape.   23. The liquid crystal device according to claim 22, wherein the electrode pattern is disposed on a first conductive layer disposed on the substrate, an insulating layer disposed on the first conductive layer, and a top portion of the insulating layer. And a second conductive layer, wherein the second conductive layer has an opening.

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